1. Field of the Invention
The present invention relates to a magnetoresistive (to be referred to as MR hereinafter) element whose direct current resistance changes in accordance with a magnetic field, and to a magnetic head using the MR element.
2. Description of the Related Art
It is typically necessary for a magnetic disk apparatus to comprise a magnetic recording medium for recording magnetic information and a magnetic head for detecting a magnetic field generated from the magnetic information in the magnetic recording medium. In the conventional magnetic head, a sensing electromagnetic inductive element for detecting the magnetic field has been widely used. Such an electromagnetic inductive type sensing element which is, however signals, low in the output voltage of reproducing magnetic recording, has been disadvantageously unsuited for high-density recording.
To overcome the disadvantage, an MR type magnetic head using an MR sensing element was invented and has lately been put to practical use.
FIGS. 10 and 11 show a conventional MR sensing element. Specifically, FIG. 10 is a plan view showing the constitution of the conventional MR sensing element. FIG. 11 is a graph showing resistance vs. magnetic field transfer curve for magnetoresistance characteristics. Description will now be given to the prior art with reference to FIGS. 10 and 11.
A conventional MR sensing element 79 comprises a sensing pattern 80 consisting of a magnetoresistive layer whose resistance changes in accordance with the direction between magnetization M applied sense current J to the sensing pattern 80. The sensing pattern 80 is made of, for example, an NiFe alloy thin layer and is of rectangular shape. The sensing pattern 80 is constructed such that effective anisotropy is oriented parallel to the longer side of the rectangle and that in order to provide the linear response characteristics of resistance changes to an external field Hs, a bias field is applied to the sensing pattern 80 in advance and the magnetization M within the sensing pattern 80 thereby forms approximately 45xc2x0 with the sense current J when Hs=0. On both sides of the sensing pattern 80, domain stabilizing layers 82, 82 are provided for making the magnetic domain structure of the sensing pattern 80 a single domain.
When the external field Hs is applied, the magnetization M of the sensing pattern 80 rotates in accordance with the magnitude of Hs. The resistance of the sensing pattern 80 then changes in accordance with an angle q of the magnetization M to the sense current J as shown in FIG. 11. In case that the external field Hs is the magnetic field of a signal from a magnetic recording medium, a high sensitivity magnetic head can be realized by electrically detecting resistance changes.
The conventional MR sensing element 79 has the sensing pattern 80 of rectangular shape. In such a sensing pattern having sides with different lengths, the demagnetic field within the pattern is not constant with respect to the direction of the magnetization M. In order words, the magnitude of the demagnetic field is small in the long axis direction and large in the short axis direction. Due to this, as shown in FIG. 11, the magnetoresistance to the external field Hs show transfer curve having a flexion 84. Thus, the linear response charatceristics of resistance changes to the magnetic field is disadvantageously low.
It is therefore the object of the present invention to provide an MR sensing element with the improved linear response characteristic of resistance changes to the magnetic field, and a magnetic head using the MR sensing element.
The magnetoresistive sensing element according to the present invention comprises:
a sensing pattern consisting of a magnetoresistive layer whose resistance changes in accordance with the direction of magnetization; and
an electrode layer for applying a sense current to the sensing pattern, wherein the sensing pattern is formed to be of substantially circular shape.
The magnetoresistive sensing element according to the present invention further comprises a domain stabilizing layer for making the magnetic domain structure of the sensing pattern a single magnetic domain, wherein
the domain stabilizing layer is provided on each side of the sensing pattern and
the electrode layer is formed on the domain stabilizing layer.
This arrangement permits the demagnetic field within the sensing pattern to be constant with respect to the magnetization direction and can thereby provide the improved linear response characteristics of resistance changes to the external field.